Absorbent articles for broad use in general have been developed mainly for use in disposal of urine. These absorbent articles have been desired to be capable of handling changes caused by various factors such as a wearer's posture, intake condition of water, and physical condition, for example, wearing posture and changes of discharge states such as amount, quality and speed of discharged urine. To securely deal with these changes, an area and a volume sufficiently larger than necessary on usual use conditions need to be imparted to the absorbent articles. On the other hand, from a viewpoint of a wearer's comfort, the absorbent articles are preferably thinner and compacter.
Considering from an aspect of absorption efficiency, the absorbent articles, which have margins in this manner, have an absorbent with a remarkably bad efficiency, and are also undesirable from a viewpoint of the wearer's comfort. In order to improve area and volume efficiencies of the absorbent articles, it is important to form the absorbent itself to be as thin and compact as possible, and further to control the flow of discharged liquid. That is, a mechanism needs to be disposed in which the discharged liquid is guided to an intended/desired position of the absorbent and the discharged liquid is uniformly distributed over the whole surface of the absorbent. The absorbent of one of the absorbent articles cannot be formed to be thinner or compacter until these considerations are made, and there has been a demand for development of the absorbent articles which have these capabilities.
There have been a large number of proposals concerning the reduction of the size of the absorbent. For example, in Japanese Patent No. 3,090,266, there is disclosed an absorbent sheet containing three components including: an absorption layer mainly comprising super absorbent polymer particles; a nonwoven fabric substrate for supporting the super absorbent polymer particles; and a binder component for bonding the super absorbent polymer particles to one another and for bonding the super absorbent polymer particles to the nonwoven fabric substrate. The nonwoven fabric substrate is constituted of a nonwoven fabric which has a multilayered structure including a diffusion layer (P) formed of a fiber layer relatively high in hydrophilicity and high in density and an acquisition layer (Q) relatively low in hydrophilicity and low in density. On the surface of the absorbent sheet, an absorption region phase (phase A) including the absorption layer and the nonwoven fabric substrate carrying the absorption layer, and a diffusion/acquisition region phase (phase B) in which the super absorbent polymer particles hardly exist and which is mainly formed of only the non-woven substrate are distributed so that the phases can be distinguished from each other.
Moreover, in Japanese Patent Application Laid-Open No. 2000-232,985, there is described a disposable incontinence liner in which an absorption sheet is disposed between a top sheet and back sheet. For the absorption sheet, there is described an absorbent sheet including: an absorption layer in which polymeric absorbent particles are bonded by microfibrillated fine fibers; and a sheet support material for supporting this absorption layer. The polymeric absorbent particles having specific weights, and the absorbent sheet having specific thickness and rigidity/softness are used.
Further in Japanese Patent No. 2,872,851, there is disclosed an absorbent article including a surface material having permeability to liquid, an absorbent having liquid holding property, and a leak preventive material having impermeability to the liquid. A part or all of the absorbent is constituted of an absorption sheet in which polymeric absorbent particles are fixed to an absorption material by an adhesive applied in a dot, linear, or curve form. For the adhesive, a 180° peeling adhesive force (JIS C2107) is not less than 500 g and not more than 4000 g. An occupying area of the applied adhesive is not less than 10% and not more than 70%.
Moreover, a absorbent sheet in which polymeric absorbent particles are mixed in high concentration in a so-called air-laid method of molding a pulp sheet by a dry process and bonded/integrated by a heat-melting binder also starts to be used in an ultrathin absorbent article.
However, although the absorbent article using the above-described absorbent sheet is thin and compact as compared with the conventional article, further improvement is still necessary with respect to the efficiency.
Additionally, as a measure for efficiently absorbing the discharged liquid into the thin absorbent, a bulky nonwoven fabric has heretofore been added as a diffusion sheet, distribution sheet, transfer sheet, or acquisition sheet to the surface of the thin absorbent. These common ideas are based on the use of the diffusion phenomenon of the liquid using capillaries among the constituting fibers. An attempt has also been made to dispose a foam or bulky opening film subjected to a surface hydrophilic treatment for temporarily trapping the liquid between a top sheet and the absorbent or in the absorbent.
The present invention has been derived from an attempt to purely incorporate a mechanical liquid distribution mechanism which is disposed in contact with a discharge port of body fluid into the absorbent article.